Roll forming machines for bending sheet metal are well known in the art. They are useful for fabricating a variety of metal products including sheet metal ducts and connectors.
Roll forming machines generally include a series of forming rolls arranged in successive forming stations along an advancing path. In operation, a piece of sheet metal is passed between top and bottom rolls of each successive forming station, wherein each forming station introduces an additional degree of bending to the metal until a desired cumulative bend in the metal is complete. U.S. Pat. No. 4,045,989 describes a roll forming machine of this type and is incorporated herein by reference.
Numerous structural variations in roll forming machines are available depending on the particular bending operation desired. For example, the number and size of the forming stations can be varied to produce the particular bent metal product desired. Various modified forming stations can also be included according to specific applications. For example, U.S. Pat. No. 4,045,989, mentioned above, describes a roll forming machine, having a first forming station which recognizes notches in the edge of a metal workpiece and thereby introduces bends to predetermined alternating metal sections between the notches. It is also known to include an idler assembly as a station along the advancing path of a roll forming machine.
The present invention is useful for any roll forming application in which it is desired to periodically make adjustments to the dimensions between the bends being made.
In the case of duct fabrication, ducts are generally produced in sections which are subsequently connected at their ends by appropriate fastening means. In order to produce the desired connections between duct sections, each duct section can be provided with roll formed hems or flanges at both ends which abut and register with corresponding structures on adjacent sections when connected. The hems or flanges are joined together, for example by cleats or corner connectors. A representative example of a duct connection system is illustrated in FIGS. 1 and 2.
U.S. Pat. No. 4,466,641 describes a duct connecting system of this type, known as the Transverse Duct Connector (TDC) system, which utilizes roll formed flanges on the ends of duct sections defining frames which are unitary or integral to the duct walls. In a preferred form of this system, upper and lower channels are formed in the flanges for receiving the edges of a corner connector. The TDC system, marketed by The Lockformer Company and Iowa Precision Industries, Inc., permits rapid connection of duct sections by snapping corner connectors into the frames and bolting the duct sections together across adjoining frames to produce a duct having superior strength. U.S. Pat. No. 4,579,375 also describes a duct connection system utilizing duct sections having integral frames.
There is a need for a more versatile roll forming machine which can easily be reset to make bends of different dimensions. For example, when forming duct sections using existing roll forming technology, the integral frames are formed of flanges having a particular fixed height. However, when ducts made from different metal weights are fabricated, correspondingly different heights of flanges are often used. In order to convert roll forming production to make duct sections having a different flange height, the apparatus must be retooled with a new outboard set of forming station rolls if possible, or if not, an altogether different machine must be used. The cost in terms of time and equipment to make the necessary adjustments, if such are feasible, can be significant. The present invention addresses these and other needs.
The roll forming apparatus of the present invention, while generally applicable to bending operations, is particularly useful for fabricating duct sections for use in these and other types of duct manufacturing systems.